Research has confirmed that multiple layers of etiological risk, including individual genetic risk, proximal environmental experiences (e.g., parenting and family relationship characteristics), and neighborhood context (e.g., neighborhood disadvantage, social organization, and exposure to community violence), influence the development of children's conduct problems (CP; aggressive and rule-breaking behaviors comprising diagnosable and sub-threshold Conduct Disorder). To date, however, we little insight into the interplay between genetic and contextual risks for child CP, or the role that proximal risks may play in this relationship. The current application outlines a novel and unique research design intended to do just this. In particular, we will sample 500 middle-to-low income child twin families that reside in one of a range of disadvantaged neighborhood contexts (i.e., from moderately to extremely disadvantaged). This at-risk twin sampling strategy constitutes a significant advance over current epidemiological twin studies in regards to studies of contextual risk, as such samples contain relatively few at-risk families. As a result, extant twin studies are typically unable to meaningfully explore the role of contextual risk as an etiological moderator of child outcome. We will then augment our innovative sampling approach with an in-depth assessment battery that includes comprehensive assessments of the twins' and the parents' psychological and behavioral profiles, videotaped parent-child and family interactions, interviews assessing exposure to community violence, questionnaires completed by the twins' teachers, and census tracking of the family's neighborhood. We will also collect an (unrelated) neighborhood informant sample to report on social organization and crime in each family's neighborhood. State-of-the-art behavioral genetic analyses will then examine both how contextual risk factors, both alone and in combination with proximal risk factors, moderate genetic predispositions for child CP. This innovative sampling and design strategy will allow us to meaningfully integrate, for the first time, the genetic, proximal, and contextual risk factors thought to underlie the development of child CP, and accordingly, has the potential to significantly advance our understanding of the origins of child conduct problems.